Micro-pipettes have traditionally been used for depositing fluid onto well-plates but they generally have a much higher drop volume than is typically desired. Since low drop volumes are desirable, operators using micro-pipettes use a “touch off” technique that is very operator dependent, thereby increasing the likelihood of cross-contamination.
Recently there has been an interest in using jetted technologies for the precision dispensing of high-value materials. Some specific examples of these applications include the printing of reagents, enzymes or other proteins into well-plates for the purpose of fluid mixing or initiating chemical reactions. Prior solutions have included continuous inkjet (CIJ) technology, which offers relatively high velocities and drop volumes. Unfortunately CIJ systems are relatively more expensive than other systems because not all printer head components are wafer-fab compatible and because of complicated ink recirculation systems. Additionally, due to the extra recirculation systems and other various components, the distance between the CIJ and the substrate is much larger than is preferred. Other technologies such as Thermal Inkjet (TIJ) and Piezo Inkjet (PIJ) drop-on-demand printheads have traditionally been limited to the jetting of colorant in imaging and marking applications. Recently there has been an interest in using TIJ and PIJ technologies in the above applications, but success has been limited. This limited success is because TIJ and PIJ technologies have mainly been designed for high quality imaging applications, not dispensing of high-value materials.